Semiconductor devices and liquid crystal display devices are fabricated by a so-called photolithography technique, wherein a pattern formed on a mask is transferred onto a photosensitive substrate. An exposure apparatus used by this photolithographic process has a mask stage that supports the mask, and a substrate stage that supports the substrate, and transfers the pattern of the mask onto the substrate via a projection optical system while successively moving the mask stage and the substrate stage. There has been demand in recent years for higher resolution projection optical systems in order to handle the much higher levels of integration of device patterns. The shorter the exposure wavelength used and the larger the numerical aperture of the projection optical system, the greater the resolution of the projection optical system. Consequently, the exposure wavelength used in exposure apparatuses has shortened year by year, and the numerical aperture of projection optical systems has also increased. Furthermore, the currently mainstream exposure wavelength is the 248 nm KrF excimer laser, but an even shorter wavelength 193 nm ArF excimer laser is also being commercialized. In addition, like resolution, the depth of focus (DOF) is also important when performing an exposure. The following equations respectively express the resolution R and the depth of focus δ.R=k1·λ/NA  (1)δ=±k2·λ/NA2  (2)
Therein, λ is the exposure wavelength, NA is the numerical aperture of the projection optical system, and k1 and k2 are the process coefficients. Equations (1) and (2) teach that shortening the exposure wavelength λ increases the resolution R, and that increasing the numerical aperture NA decreases the depth of focus δ.
If the depth of focus δ becomes excessively small, then it will become difficult to align the surface of the substrate with the image plane of the projection optical system, and there will be a risk of insufficient margin of focus during the exposure operation. Accordingly, a liquid immersion method has been proposed, as disclosed in, for example, Patent Document 1 below, as a method to substantially shorten the exposure wavelength and increase the depth of focus. This liquid immersion method fills a liquid, such as water or an organic solvent, between the tip surface (lower surface) of the projection optical system and the surface of the substrate, thus taking advantage of the fact that the wavelength of the exposure light in a liquid is 1/n that of in air (where n is the refractive index of the liquid, normally approximately 1.2-1.6), thereby improving the resolution as well as increasing the depth of focus by approximately n times. The disclosure of the following pamphlet is hereby incorporated by reference in its entirety to the extent permitted by the national laws and regulations of the designated states (or elected states) designated by the present international patent application.
[PATENT DOCUMENT 1] International Publication WO99/49504
Incidentally, although nozzles are used for the supply and collection of the liquid in the abovementioned related art, there is a possibility that the pattern image projected onto the substrate via the projection optical system and the liquid will degrade if vibrations produced by the nozzles are transmitted to, for example, the projection optical system. In addition, there is also a possibility that the position of the nozzles will fluctuate due to changes in the pressure of the liquid, and there is also a possibility that it will become difficult to supply and collect the liquid in the desired state.